1. Field of the Invention
The present invention relates to data storage networks, and especially networks implementing SAN (Storage Area Network) functionality or the like. More particularly, the invention concerns server-free transfers of data between storage devices in a data storage network environment.
2. Description of the Prior Art
By way of background, data storage networks, such as SAN systems, provide an environment in which data storage peripherals are managed within a high speed network that is dedicated to data storage. Such networks often include a data storage manager server that handles data storage requests (e.g., copy, backup, etc.) from data client nodes (data clients) that are connected to the storage manager server via a conventional LAN (Local Area Network) or WAN (Wide Area Network). Within the data storage network, the storage manager server generally has access to all devices within the pool of peripheral storage, which may include any number of interconnected magnetic disk drive arrays, optical disk drive arrays, magnetic tape libraries, etc. In all but the smallest data storage networks, the required inter-connectivity is provided by way of arbitrated loop arrangements or switching fabrics, with the latter being more common.
There are facilities within the data storage network environment that a storage manager server conventionally uses to delegate the work of moving data between storage devices. For example, the SCSI-3 (small computer storage interface) extended copy command provides a means to copy data from one set of logical storage units in the data storage network to another set of logical storage units under the control of the storage manager server, but with the actual data transfer operations being performed by a “data mover” entity within the data storage network. This “server-free” data movement is performed by the data mover at the request of the storage manager server. All that is required of the storage manager server is to prepare the data source and destination devices and then prepare and issue the extended copy command to the data mover. Because it is not performing the actual data transfer operations, the storage manager server is free to handle more concurrent client connections and server operations.
The SCSI-3 extended copy command is conventionally composed of many “copy orders” that specify the source and destination storage devices (targets), and the data blocks to be transferred from each source target to each destination target. A problem that arises in this environment is that the entity which knows the source targets may not be the same entity that knows the destination targets. A third entity may be responsible for data manipulations such as compression, encryption and check data generation. These entities could be different pieces of a program or could be located on different computer systems. One party may not know what the other party knows, and the parties may not necessarily trust each other. This makes it difficult to create a copy order which has to have both the source target and the destination target specified for each data block to be transferred. Another problem is that it is difficult to provide the aforementioned data manipulations. With present capabilities, such transformations would have to be separately specified for each data source and destination target.
It is to solving the foregoing problems that the present invention is directed. In particular, what is required is an alternative system and method for handling server-free data transfers in which data copy commands may be formulated by entities that do not necessarily have complete knowledge of both the source and destination targets. An additional goal is to provide a system and method wherein data transformations such as compression, encryption and check data generation may be provided without knowledge of the characteristics of both targets involved in the data transfer.